1. Field of the Invention
This invention relates to apparatus for identifying conductors in a multiconductor cable and for testing the conductors for shorts and continuity, and more particularly to such apparatus for testing the cable after it is installed in a vessel or like environment in which the ends of the cable are remote from one another.
2. Description of the Prior Art
The known prior art is replete with systems for testing conductors in a multiconductor cable and for identifying opposite ends of each conductor or conductor pair.
One general scheme disclosed in the prior art employs an electronic or electromechanical stepper to apply a test signal to each conductor in a multiconductor cable at the central office end of the cable. A remote unit supplied with a counter or a signal detector responds to a signal received on one conductor to identify the conductor and/or test the conductor. Exemplifying such scheme are the following U.S. Pat. Nos. 3,252,088; 3,287,509; 3,288,943; 3,476,888; 3,740,644; 3,742,350; 3,891,811; 3,976,939 and 3,986,106.
Another category of prior art testing apparatus includes two units, one of which is connected to each end of a cable. Each of the units has a counter and the counters are synchronized with one another through a spare conductor in the cable. Accordingly, the counters cycle through all conductors in synchronism and afford identification of opposite ends of the conductors and in some cases testing of the electrical condition of the conductors. Exemplifying this prior art system are U.S. Pat. Nos. 3,288,945; 3,427,538 and 3,514,552.
Still another form of prior art cable testing apparatus employs a sequencer at one end which applies a test signal to the cable conductors in sequence, a circuit having a probe adapted for connection to a single conductor at the other end of the cable and an interconnection so that when the conductor to which the probe is connected is addressed by the sequencer, the sequencer is automatically stopped until the conductor can be tagged or otherwise identified. Exemplifying this type of equipment are U.S. Pat. Nos. 3,401,238; 3,559,055; 3,681,686 and 3,699,438.
The prior art also discloses various circuits for testing individual conductors in a wiring harness. These systems are not applicable to testing cables in which the ends of the cables are remote from one another. Harness testing systems are disclosed in U.S. Pat. Nos. 3,600,673; 4,030,029 and 4,257,002.
U.S. Pat. No. 3,644,687 discloses a system in which there is a central office stepper capable of applying a test signal to each cable conductor in turn and a remotely located field unit which enables the user to advance the stepper at will. The stepper puts an audio tone on the conductor to which it is connected and the tone is located by a probe at the remote location.
U.S. Pat. No. 3,902,026 discloses a sophisticated system employing a random access memory at one end of the cable. Coded pulses indicative of the conductor number are transmitted from a remote end of the cable, and the coded pulses are stored at an address in the random access memory that corresponds to the position of the cable termination on a terminal board associated with the random access memory.
U.S. Pat. No. 4,074,187 discloses a cable tester having a plurality of light emitting diodes (LEDS) which are included in a circuit such that the number and identity of LEDS that are illuminated provide an indication whether the conductor to which the system is connected is shorted, open, grounded or trouble-free.
German Offenlegungsschrift 26 26 727 discloses a cable tester having a pulse generator constructed from integrated circuit TTL logic modules arranged in a shift register so that a test signal can be applied to each conductor in turn. There is a receiving unit having an LED connected to each conductor so that the identity of the LED that is illuminated provides identification of a particular conductor.